Calmodulin (CaM) is a ubiquitous regulatory protein that communicates the presence of calcium to its molecular targets and correspondingly modulates their function. This key signaling protein is important for controlling the activity of hundreds of membrane channels and transporters[1]. CaM contains two globular domains each containing a pair of helix-loop-helix Ca²⁺-binding sites (EF-hands). Upon Ca²⁺ binding, conformational transitions in calmodulin are induced that changes its affinity to target proteins[1]. One example of the proteins function being regulated by CaM is the family of auqaporins (AQPs): water channels that facilitate the flux of water molecules across membranes. Regulation of the water permeability by CaM is achieved through a Ca²⁺-dependent interaction between Ca²⁺-CaM and the cytoplasmic C-terminal domain of the AQP[2].